CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Revenue		$ 311,999	$ 208,768	$ 127,049
Cost of revenue	[1]	93,900	67,184	46,047
Gross profit		218,099	141,584	81,002
Operating expenses:
Research and development	[1]	91,067	62,615	36,403
Sales and marketing	[1]	166,987	114,052	77,875
General and administrative	[1]	64,371	47,902	32,869
Total operating expenses	[1]	322,425	224,569	147,147
Operating loss		(104,326)	(82,985)	(66,145)
Other income (expense), net		1,520	(729)	(1,533)
Loss before provision for (benefit from) income taxes		(102,806)	(83,714)	(67,678)
Provision for (benefit from) income taxes		993	338	(263)
Net loss		(103,799)	(84,052)	(67,415)
Accretion of redeemable convertible preferred stock		0	0	(18)
Net loss attributable to common stockholders		$ (103,799)	$ (84,052)	$ (67,433)
Net loss per share attributable to common stockholders, basic and diluted (usd per share)		$ (1.11)	$ (0.99)	$ (1.26)
Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted (in shares)		93,161	84,926	53,571

[1] Includes share-based compensation expense as follows as of December 31, 2016, 2015, and 2014:Cost of revenue: $7,045, $4,541, $2,464Research and development: $27,083, $19,414, $10,918Sales and marketing: $23,043, $14,759, $10,680General and administrative: $16,608, $13,842, $8,077